This invention relates generally to cardiopulmonary resuscitation defibrillation and monitoring apparatus and, more particularly, to a combination cardiac compressor, lung ventilation, defibrillator and heart monitor apparatus.
External cardiac compression can be effectively employed for obtaining perfusion by causing forced pumping of blood from a temporarily stopped heart. This is achieved by constant cyclic external compression of the heart (systole) for a short time period followed by pressure release to allow heart expansion (diastole) for a short time period. To achieve proper heart compression by external force, the breast bone is forced toward the backbone of the patient while the patient's back is rigidly supported.
Although forced pumping of blood is essential for a patient whose heart has stopped, this is only part of the continuous treatment necessary, since when the heart stops, breathing stops also. Hence, when external mechanical or manual cardiac compression is presently employed, simultaneous, sustained cyclic, mechanical or mouth to mouth ventilation is also important to cyclically inflate the lungs for oxygenization of the blood. According to accepted medical practice, the lungs are ventilated or inflated during the diastole period of the compression cycle. Whether carried out mechanically or manually, these techniques comprise what is commonly referred to as cardiopulmonary resuscitation or CPR. However, CPR is only supportive therapy designed merely to maintain cell viability or structure. CPR alone will normally not restart a heart that has stopped or which is in ventricular fibrillation. Definitive therapy such as defibrillation by electrical shock is normally necessary to restart the normal functioning of the heart.
In the prior art, certain disadvantages existed when such supportive and definitive therapy were combined. When applying supportive therapy, it is extremely important that there be no interruptions. In the case of manual CPR where chest compression is being performed manually by the application of force by the rescuer's hands, interruptions are presently necessary to monitor the patient's EKG and to apply electrical defibrillation shocks. In the first case, supportive therapy must be interrupted because of distortion in the patient's EKG produced by the rescuer. This distortion or noise is generated from the rescuer's own EKG and from electrical signals generated in the rescuer's muscles as he applies chest compression. This distortion or noise is high enough to completely obscure the patient's EKG and must be interrupted during the time that the patient's EKG is being assessed. This is an interruption which is inevitable in the manual CPR technique. Furthermore if the patient requires electrical defibrillation, then at that time, in the manual technique, the hands must be taken off because of the risk of giving a shock to the rescuer. Also, generally speaking, after a heavy external defibrillation shock, a substantial time period must pass before the oscilloscope and the circuitry within the oscilloscope or chart of the EKG monitor returns to normal. Sometimes it takes several seconds for the equipment to clear and provide a check on the electrical activity of the patient's heart and during this time, the patient is left unsupported.
When using one of the many standard commercially available mechanical massagers, there is often room on the chest to place defibrillation paddles while external cardiac compression is being performed. If the compressor is pneumatic rather than electrically driven, distortion in the patient's EKG is minimal and a useful signal can be obtained without interruption in supportive therapy. Thus, it is possible to give defibrillation shocks while such a CPR unit is running. However, for some reason there has been a reluctance on the part of the rescuers to use this technique, and rescuers in the past have had a tendency to shut the CPR unit off during defibrillation and monitoring. This is probably due to the fact that the rescuer carrying out the operation would be standing over the patient with some risk of his being in contact with the equipment or with the patient. Thus, even though distortion caused by pneumatically driven CPR equipment is minimal and the signal normally obtained during CPR is adequate to make a judgment as to whether the patient is in cardiac arrest or not, many rescuers insist on shutting off CPR equipment during defibrillation and monitoring.
The most common definitive therapy in the prior art is the use of a defibrillation shock for restarting a heart that has stopped or a heart that has gone into ventricular fibrillation. However, the conventional external electrodes used in the prior art are placed on the patient's chest and a disproportionately large amount of the current applied to the patient's chest never flows through the heart. Accordingly, the power requirements of prior art defibrillators are quite high and most prior art units are bulky and ill-suited to portability. Thus, it is often not possible to apply such definitive therapy to the patient until the patient has reached a hospital. Furthermore, since a disproportionate amount of energy must be applied to the patient's chest to cause that small percentage of electrical energy flowing through the heart to be sufficient to defibrillate the heart, electrical defribrillation, as carried out in the prior art, with external electrodes, is a traumatic event both for the heart and other portions of the patient's body.
Front to back defibrillation techniques are found in the prior art wherein first and second defibrillator electrodes are disposed anterior and posterior to the patient's heart on the patient's chest and back, respectively. However, none of these arrangements provide for simultaneous application of the cardiac massage because of the danger of shock to the individual applying compressive force to the patient's chest, and without simultaneous cardiac compression these defibrillation techniques provide no substantial reduction in the power of the defibrillation shock applied. Furthermore, these arrangements do not solve the aforementioned problem of interrupting supportive techniques during monitoring or defibrillation.